Tuning the properties of copper(II) complexes with tetra- and pentadentate bispidine (=3,7-diazabicyclo[3.3.1]nonane) ligands

The synthesis of a series of tetra- and pentadentate bispidine-type ligands (bispidine = 3,7-diazabicyclo[3.3.1]nonane) - tetradentate ligands are donor-substituted at C(2) and C(4), pentadentate ligands have an additional donor at N(3) or N(7), with pyridine, 2-methylpyridine, or quinoline donor moieties - and of their Cu-II complexes are reported, together with single-crystal structural analyses and solution studies (electrochemistry, electronic and EPR spectroscopy). Depending on the ligand geometry and on the co-ligands (solvent or counter anion), there are various structural forms (pseudo-Jahn - Teller elongation along all three molecular axes), and the structural data are correlated with the spectroscopic and electrochemical parameters.